Donald Trump’s effort to end the controversy he helped stoke over President Obama’s citizenship has handed Democrats a fresh opportunity to motivate voters, particularly African Americans, who are offended by an issue that had faded to the recesses of the campaign.

Black lawmakers, who listened to Obama gleefully mock the Republican nominee’s evolving views on his birth certificate during a gala dinner Saturday night, plan to take their condemnation of Trump on the road in the coming weeks.

Democrats are already fundraising off the issue. They seized on the topic during the Sunday talk shows. And Trump’s opponent, Hillary Clinton, is widely sharing views on the topic from her supporters and newspaper editorials.

“This isn’t just a wacky guy saying something wacky,” Clinton’s running mate, Sen. Tim Kaine of Virginia, said on CNN’s “State of the Union.” Explaining the pre-Civil War period when blacks were not considered U.S. citizens, Kaine said: “When Donald Trump says that the first African American president is not a citizen, that is so painful to so many people who still have deep feelings about that dark chapter in American life.”

The resurrection of the “birther” issue comes as polls have shown a tightening race between Clinton and Trump and Democrats are worried about turnout among black voters — a key constituency that helped fuel Obama’s historic wins in 2008 and 2012.

Donald Trump, the 2016 Republican presidential nominee, spoke at the Trump International Hotel in Washington on Friday, where he declared, after years suggesting the opposite, that President Obama was born in the U.S. (Andrew Harrer/Bloomberg)

Fresh attention to Trump’s long-running and false accusations questioning Obama’s citizenship could also inspire others from the “Obama coalition,” which included young voters, Hispanics and college-educated whites, to turn out for less-popular Clinton.

“For a lot of people, it’s brought up that anger again, and that anger is not going to dissipate before the election,” said Kweisi Mfume, a former congressman from Maryland and former president of the NAACP. “This is another reason to get up and vote against Donald Trump.”

Campaigning on Clinton’s behalf in Cleveland on Sunday, Sen. Elizabeth Warren (D-Mass.), a darling of the party’s left wing, was even more blunt.

“For years, Donald Trump led the charge on the birther movement,” she said. “Only when his handlers tied him down and made him did he finally admit that it wasn’t true. What kind of man does that? A man with a dark and ugly soul.”

Trump’s aim on Friday was to put the issue behind him by declaring that “President Barack Obama was born in the United States. Period.” That view contradicted multiple Trump statements over the past five years; he also added to the controversy by claiming that Clinton and her campaign started the birther movement during the 2008 nominating contest against Obama. He took credit for forcing Obama to offer proof of his citizenship.

Trump’s surrogates continued to push those views on the Sunday talk shows, and they also tried to argue that there was no need to keep talking about the issue. Democrats, they argued, were doing so only to deflect from Clinton’s slide in the polls.

“The birther issue is a done issue,” New Jersey Gov. Chris Christie (R), Trump’s transition chairman, said on CNN. “If you think that anyone is going to vote for either Donald Trump or Hillary Clinton or against either one of them based upon this issue, then I think there’s a fundamental misunderstanding of the concerns of the American people. Let’s move on to the real issues.”

Pence said there are news reporters who trace the “birther movement all the way back to Hillary Clinton’s campaign in 2008” and that “the facts speak for themselves,” although he wouldn’t list any such facts.

At one point, ABC’s Martha Raddatz asked Pence: “Why did it take him so long to put it to an end?”

“It’s over,” Pence responded.

To that, Raddatz said: “It’s not over.”

Obama clearly wasn’t ready to move on Saturday night during his final appearance before an annual dinner hosted by the Congressional Black Caucus Foundation in Washington.

The president began his remarks by saying sarcastically that he had “an extra spring in my step” given that Trump had finally acknowledged that he is an American citizen.

“And to think with just 124 days to go, under the wire, we got that thing resolved,” Obama said to laughter from the predominantly African American audience. “In other breaking news, the world is round, not flat.”

The president used the balance of a feisty speech to urge black voters to turn out in large numbers for Clinton, saying it would be “a personal insult” to him if they don’t help carry out his legacy by electing his choice for president.

Rep. Gregory W. Meeks (D-N.Y.), who was among those in the audience, said that members of the Congressional Black Caucus are preparing to travel to presidential battleground states including Ohio, North Carolina and Florida to make the case against Trump and for Clinton. The birther comments will feature prominently in the effort, he said.

“The birther issue is the straw that broke the camel’s back,” said Meeks, who chairs the group’s political action committee. “I think the closer we get to Election Day, the more enthusiasm there will be.”

Within hours of Trump’s comments on Friday, the group of black lawmakers had already mobilized to hold a news conference during which, one after another, they condemned Trump.

“We will not elect a chief bigot of the United States of America,” said Rep. Sheila Jackson Lee (D-Tex.).

“Donald Trump is nothing more than a two-bit racial arsonist,” said Rep. Hakeem Jeffries (D-N.Y.).

“He’s a hater. He’s a bigot and he’s racist,” said Val Deming, a former Orlando police chief running for Congress in Florida. “I’ve learned as a law enforcement officer to call it like I see it.”

Clinton, who has stopped short of calling Trump a “racist,” has stepped up her criticism of the birther issue as well, saying Friday that “he has led the birther movement to delegitimize our first black president” and “there is no erasing it in history.”

Her campaign issued news releases with high-profile supporters from key swing states, including Virginia and Florida, chastising Trump for his past views. The Clinton campaign also widely circulated editorials from newspapers in North Carolina and Pennsylvania that were critical of the latest episode with Trump.

The arm of the party that helps elect Democrats to Congress was already focused on making Trump an issue in swing districts, pushing Republicans to say whether they agree with divisive statements the Republican nominee has made.

On Friday, the group fired off a fundraising letter referring to Trump as “this racist man,” part of an effort to inspire Obama loyalists to step up contributions.

Democrats also hope that younger voters, many of whom are not fired up about Clinton, can be motivated by wanting to stop Trump from reaching the White House.

During a Saturday swing through northeast Ohio, Bernie Sanders reminded two audiences, largely composed of college students, that Trump had spent years questioning the president’s citizenship.

“You cannot elect a president of the United States whose campaign is based on bigotry,” said Sanders, the runner-up in this year’s Democratic primaries, at Kent State University. “What they were trying to do, led by Donald Trump, was delegitimize the presidency of the first black president we’ve ever had.”

There has been evidence that such arguments are already resonating.

At a Sunday rally headlined by Warren, several black women in attendance noted that Trump did not apologize Friday for pushing a discredited theory about Obama for five years.

“They should have insisted that he apologize,” said Annie Thompson, 76.

“It was so disrespectful,” said Carolyn Starks, 70. “Hatred follows that man wherever he goes.”

Trump’s argument that Clinton had secretly been responsible for the birther conspiracy fell just as flat.

“Lie, lie, lie,” said Starks. “People that lie all the time like that — I think they have mental problems.”

Jenna Johnson in Washington and David Weigel in Cleveland and Kent, Ohio, contributed to this report.